Electrically-conducting adhesion-promoters on conductive plastic

ABSTRACT

Disclosed are methods for enhancing the adhesion of composite electrodes onto conductive plastic foils (e.g., current collectors). Also disclosed are electrochemical cells produced from these foils.

This application is a continuation of application Ser. No. 07,968,172,filed Oct. 29, 1992 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to methods for enhancing the adhesion ofcomposite electrodes onto conductive plastic foils useful as currentcollectors, to the foils prepared by these methods and toelectrochemical cells produced from these foils.

2. State of the Art

Electrochemical cells comprise a cathode, an anode and an electrolyteinterposed therebetween. The electrochemical cells are often defined asliquid or solid cells and this refers merely to whether the electrolyteinterposed between the anode and the cathode is a liquid or a solid.Solid electrochemical cells are well known in the art and present manyadvantages over conventional liquid batteries such as improved safetyfeatures, lighter weight, etc.

In order to enhance the overall current produced by solid or liquidbatteries, it is conventional to employ several electrochemical cells ina battery. When so employed, the current from each of the cells isaccumulated so that the total current generated by the battery isroughly the sum of the current generated from each of the individualelectrochemical cells employed in the battery.

One method for accumulating the current from individual electrochemicalcells is by using a current collector attached to the cathode or theanode of the electrochemical cell. Typically, the current collector is ametal foil or a conductive plastic which is coupled to other currentcollectors in the battery so that the current generated by each cell iscollected and accumulated over all of the cells. Thus, the total currentgenerated by the battery is a summation of the current generated by eachof the electrochemical cells employed in the battery minus whatevercurrent is lost due to resistance in the current collector.

Notwithstanding the benefits of using current collectors inelectrochemical cells, metal foil current collectors are heavier thanconductive plastic foil current collectors and adversely increase theweight of the battery. On the other hand, when conductive plastic foilsare used as the current collector, they are in direct contact with acomposite electrode and are suspectable to swelling due to contact ofthe current collector with the electrolytic solvent found in theelectrode. Such swelling adversely affects the performance of thebattery.

Additionally, some conductive plastic foil current collectors possess arelatively non-adherent surface which retards the attachment of acomposite electrode to the surface of the current collector.Specifically, composite electrodes are typically prepared from a pastewhich is applied onto the surface of the current collector byconventional means such as extrusion and then cured to form a solidcomposite electrode. When the surface of the current collector isnon-adherent, then during application of a paste onto the foil, thepaste can become dislodged from the foil. In turn, after curing, suchdislodgement will result in defects in collecting current from thatcell.

This invention is directed to the discovery that the inclusion of alayer of electrically-conducting adhesion-promoter to the surface ofconductive plastic foil current collector provides a means to bothincrease the adherence of the electrode to the foil and to retardcontact of the electrolytic solvent with the plastic foil.

Thus, while the art discloses that polymers containing grafted acidfunctionalities (i.e., maleic acid or anhydride) have improved adherence(see U.S. Pat. Nos. 4,810,755 and 4,857,600 as well as InternationalPatent Application Publication No. WO 91/02760), there is nothing in theart which discloses the use of a layer of an electrically-conductiveadhesion promoter to the surface of the plastic foil.

SUMMARY OF THE INVENTION

This invention is directed to the novel and surprising discovery thatthe surface of conductive plastic foil current collectors can bemodified to be more adherent to an electrode paste by placing a layer ofan electrically-conducting adhesion-promoter onto the surface of thecurrent collector which is to be interposed between the foil and theelectrode paste.

Additionally, because this layer of electrically-conductingadhesion-promoter is interposed between the composite electrode and theconductive plastic current collector, contact of the composite electrodewith the conductive plastic current collector is prevented. This, inturn, retards any contact of the electrolytic solvent in the compositeelectrode with the current collector thereby inhibiting swelling of theconductive plastic current collector.

The electrically-conducting adhesion-promoter is a solid polymeric layerwhich comprises an effective amount of a conductive material so as torender the polymeric layer conductive, a polymer and acidfunctionalities. Without being limited to any theory, it is believedthat the acid functionalities of the solid polymer composition providein situ for adhesive/binding functionalities which, when contacting theconductive plastic foil, enhance the adherence of the foil to theadhesion-promoter layer. Additionally, the surface of thisadhesion-promoter layer is characterized on a microscopic level by peaksand valleys rather than a smooth planar surface and, accordingly,provides an adherent surface for the composite electrode.

Surprisingly, the inclusion of an effective amount of a conductivematerial in the polymeric layer does not interfere with the enhancedadherence of this layer to the conductive plastic foil.

In view of the above, in one of its composition aspects, this inventionis directed to a conductive plastic foil containing on one of itssurfaces a layer of an electrically-conducting adhesion-promotercomprising:

from about 30 to 80 weight percent of a conductive material;

from about 20 to about 70 weight percent of a prepolymer or polymerthereof;

and an effective amount of acid functionalities so as to enhance theadherence of this layer of electrically-conducting adhesion-promoter tothe surface of the conductive plastic foil.

Upon application to the surface of the conductive plastic foil currentcollector, this layer is typically a paste or a colloidal suspensionwhich is applied onto the foil by conventional application techniquessuch as extrusion, roll coating, etc.

Pastes and colloidal suspensions are formed by conventional techniques.For example, prepolymers are typically liquids which, when combined withrequisite amounts of conductive material, form a paste or colloidalsuspension suitable for application onto a conductive plastic foil.Conventional curing techniques then transform the paste or colloidalsuspension to a solid polymeric matrix on the surface of the foil.

On the other hand, polymers can be dissolved into a compatible solventor melt at an elevated temperature to provide a liquid ("hot-melted").When combined with requisite amounts of conductive material, the liquidforms a paste or colloidal suspension suitable for application onto theconductive plastic foil current collector. Removal of the solvent orcooling of the melted polymer results in the formation of a solidpolymeric matrix on the surface of the foil.

In another of its composition aspects, this invention is directed to anelectrode/current collector comprising

a conductive plastic foil suitable for use as a current collector,

a layer of a solid polymeric matrix, electrically-conducting,adhesion-promoter formed on at least one surface of the foil whichcomprises from about 30 to 80 weight percent of a conductive material;from about 20 to about 70 weight percent of a polymer derived from asolid matrix forming monomoer or partial polymer thereof; and aneffective amount of acid functionalities so as to enhance the adherenceof this layer of electrically-conducting adhesion-promoter to thesurface of the foil; and

a composite electrode.

In another of its composition aspects, this invention is directed to anelectrochemical cell comprising:

a conductive plastic foil suitable for use as a current collector,

a layer of a solid polymeric matrix, electrically-conducting, adhesionpromoter comprising from about 30 to 80 weight percent of a conductivematerial; from about 20 to about 70 weight percent of a polymer derivedfrom solid matrix forming monomer or partial polymer thereof; and aneffective amount of acid functionalities so as to enhance the adherenceof this layer of electrically-conducting adhesion-promoter to thesurface of the foil;

a composite cathode;

an electrolyte; and

an anode;

wherein the layer of said solid polymeric matrix,electrically-conducting, adhesion promoter is interposed between thefoil and the composite cathode and further wherein the electrolyte isinterposed between the composite cathode and the anode.

In one of its method aspects, this invention is directed to a method formodifying the surface of a conductive plastic foil current collector torender it more adherent to a composite electrode and less suspectible toswelling when contacting a composite electrode which method comprises:

(a) selecting a conductive plastic foil suitable for use as a currentcollector;

(b) applying a layer of an electrically-conducting adhesion-promoteronto said foil which layer comprises:

from about 30 to 80 weight percent of a conductive material;

from about 20 to about 70 weight percent of a compound selected from thegroup consisting of a solid matrix forming monomer, a partial polymer ofa solid matrix forming monomer, a hot-melt polymer derived from a solidmatrix forming monomer or partial polymer thereof, and a solutioncomprising a polymer derived from a solid matrix forming monomer orpartial polymer thereof; and

an effective amount of acid functionalities so as to enhance theadherence of this layer of electrically-conducting adhesion-promoter tothe surface of the foil, and

(c) converting the layer formed in step (b) above to a solid polymericmatrix, electrically-conducting, adhesion-promoter layer.

Preferably, the acid functionalities are selected from the groupconsisting of carboxylic groups (--COOH) and sulfonic groups (--SO₃ H).

The electrolyte employed in the electrochemical cell is either a liquidor solid electrolyte but preferably is a solid electrolyte.

Preferably, the layer of solid polymeric matrix,electrically-conducting, adhesion-promoter is no more than 100 microns(μm) in thickness and more preferably is from about 100 Angstroms toabout 20 μm in thickness and even more preferably is from about 0.1 μmto about 10 μm in thickness.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, this invention is directed, in part, to conductiveplastic foil current collectors which have been modified so as toimprove their adherence properties to a composite electrode and toretard contact of the electrolytic solvent with the plastic foil.However, prior to describing this invention in further detail, thefollowing terms will first be defined.

DEFINITIONS

As used herein, the following terms have the following meanings.

The term "conductive plastic foil" refers to any plastic foil which hasbeen doped with a sufficient amount of a conductive material so as to beconductive and therefore act as a current collector in anelectrochemical cell. Suitable conductive plastic foils are well knownin the art and include, by way of example, commercially availableconductive plastic foils such as those available from SouthwallTechnologies, Palo Alto, Calif. under the tradename SOUTHWALL SILVERREFLECTOR FILM. Other conductive plastic foils are commerciallyavailable from Graphics Technology International, South Hadley, Mass.

The particular conductive plastic employed is not critical and include,by way of example, polyesters, polycarbonates, polyacrylates,polyethylenes, polypropylenes and the like. Typically, the plastic is ofsufficient molecular weight to impart structural rigidity to theplastic. Preferably, the plastic has a molecular weight of at leastabout 10,000 and more preferably, from about 10,000 to about 5,000,000.

The plastic is doped with a sufficient amount of a conductive materialto render the plastic conductive. Such conductive materials include, byway of example, carbon powder, graphite, powdered nickel, metalparticles, conductive polymers (i.e., characterized by a conjugatednetwork of double bonds like polypyrol and polyacetylene), and the like.

The conductive plastic can be continuous and cover the entire surface ofthe current collector or non-continuous and not cover the entire surfaceof the current collector. Examples of non-continuous current collectorsinclude non-conductive plastics having conductive plastic tabs insertedtherein wherein the tabs act as the current collector.

The term "solid polymeric matrix" refers to a material which iscompatible with acid functionalities and which is formed by polymerizinga prepolymer (as defined below) and, when used in combination with aneffective amount of a conductive material, is conductive. The solidpolymeric matrix may or may not be ion-conducting but, preferably, isnot ionically conducting (i.e., does not conduct alkali metal oralkaline earth metal cations).

The term "compatible with acid functionalities" means that the presenceof acid functionalities in the solid polymeric matrix neither rendersthe solid polymeric matrix unsuitable for use in electro-chemical cellsnor results in a significant degradation of the solid matrix.

The term "a solid matrix forming monomer" refers to organic materialswhich in monomeric form can be polymerized to form solid polymericmatrices and which are electrically conducting when combined with aneffective amount of a conductive material and further which, whenpolymerized, are compatible with acid functionalities. Suitable solidmatrix forming monomers are well known in the art and the particularmonomer employed is not critical.

Preferably, the solid matrix forming monomers do not contain hetero atomfunctionalities capable of forming donor acceptor bonds with inorganiccations so as to render the solid matrix ion-conducting (i.e., able toconduct alkali metal or alkaline earth metal cations). Ion-conductinghetero atom functionalities in solid polymeric matrices include, by wayof example, ether groups, amine groups, and the like. On the other hand,hetero atom functionalities such as carboxylic acid groups, sulfonicacid groups, etc., are not ion-conducting in solid polymeric matricesbecause these functionalities bind too tightly with the cations.

Examples of suitable solid matrix forming monomers include, by way ofexample, acrylic acid (CH₂ =CHCOOH), chloroacrylic acid (ClCH=CHCOOH),bromoacrylic acid (BrCH=CHCOOH), crotonic acid (CH₃ CH=CHCOOH),propylene (CH₃ CH=CH₂), ethylene (CH₂ =CH₂), butylene (CH₃ CH₂ CH=CH₂),ethyleneimine ##STR1## acryloyl-derivatized polyalkylene oxides (asdisclosed in U.S. Pat. No. 4,908,283), urethane acrylate, vinylsulfonate polyalkylene oxides (as disclosed in U.S. Ser. No. Pat. No.5,262,253 which patent is incorporated herein by reference in itsentirety), and the like as well as mixtures thereof.

The term "a partial polymer of a solid matrix forming monomer" refers tosolid matrix forming monomers which have been partially polymerized toform reactive oligomers. Partial polymerization may be conducted for thepurpose of enhancing the viscosity of the monomer, decreasing thevolatility of the monomer, and the like. Partial polymerization isgenerally permitted so long as the resulting partial polymer can befurther polymerized to form solid polymeric matrices.

The term "prepolymers" refers to solid matrix forming monomers and/orpartial polymers thereof.

The term "acid functionalities" refers to art recognized acid containingfunctional groups capable of covalently binding to an organic residue(i.e., a hydrocarbyl group) including, by way of example, carboxylicacid groups (--COOH), sulfonic acid groups (--SO₃ H), and the like.

The acid functionalities can be incorporated directly into the solidpolymeric matrix either as a homopolymer (e.g., polyacrylic acid) or asa copolymer, terpolymer, etc. wherein at least one of the components ofthe copolymer, terpolymer, etc. is a solid matrix forming monomercontaining acid functionality (e.g., acrylic acid, vinyl sulfonic acid,etc.). Depending upon the particular monomers, the copolymers,terpolymers, etc. employed can be random copolymers, terpolymers, etc.or can be blocked copolymers, blocked terpolymers, etc.

The polymer in the solid polymeric matrix can also be derivatized tocontain acid functionality. For example, maleic anhydride, acrylic acidor methacrylic acid and the like can be grafted onto a polymer via afree-radical reaction and subsequent hydrolysis will provide forcarboxylic acid functionality on the polymer. See, for example, U.S.Pat. Nos. 4,810,755 and 4,857,600 and International application No. WO91/02760 which are incorporated herein by reference in their entirety.

Alternatively, the solid polymeric matrix can employ a mixture ofpolymers wherein at least one of the polymeric components of the mixturecontains acid functionality (e.g., a mixture of polyacrylic acid andpolyethylene) or can employ a mixture of a non-acid containing polymeror polymers and a non-polymeric acid component. In this regard, thenon-polymeric acid component preferably has a boiling point of greaterthan about 80° C. and is compatible with the polymer.

Compatible non-polymeric acid components are those which are misciblewith the polymer and do not readily diffuse from the layer ofelectrically-conducting adhesion-promoter into the electrode.Preferably, the non-polymeric acid component is substantiallynon-diffusive into the electrode and more preferably has a diffusioncoefficient into the electrode of less than 10⁻⁶ centimeters² / second.

The particular non-polymeric acid component employed is not critical andincludes, by way of example, abietic acid, decanoic acid, stearic acid,linolenic acid, palmitic acid, oleic acid, succinic acid, maleic acid,menadiol diphosphoric acid, phthalic acid, 1-hexadecane sulfonic acid,etc. Preferably, the acid containing component is represented by theformula R(COOH)_(n) wherein R is a hydrocarbyl group of from 3 to 50carbon atoms and n is an integer from about 1 to 7.

The term "cured" or "cured product" refers to the treatment of theprepolymer under polymerization conditions (including cross-linking) soas to form a solid polymeric matrix. Suitable polymerization conditionsare well known in the art and include by way of example, heating themonomer, irradiating the monomer with electron beams, and the like, etc.The resulting cured product is preferably free of hetero atom functionalgroups which are capable of conducting inorganic cations.

The term "inorganic cations" refers to the cationic portion of aninorganic salt which is suitable for use in an electrolyte and in thecomposite electrodes of an electrochemical cell. The particularinorganic ion salt employed is not critical and examples of suitableinorganic ion salts include, by way of example, LiClO₄, LiI, LiSCN,LiBF₄, LiAsF₆, LiCF₃ SO₃, LiPF₆, NaI, NaSCN, KI, CsSCN, AgNO₃, CuCl₂,Mg(ClO₄)₂ and the like. The inorganic cation is preferably selected fromthe group consisting of Li, Na, K, Cs, Ag, Cu and Mg.

The term "electrolytic solvent" refers to the solvent (i.e.,plasticizer) added to the composite electrode and the electrolyte forthe purpose of solubilizing inorganic ion salts during operation of theelectrochemical cell. The solvent can be any low volatile aprotic polarsolvent. Preferably, these materials are characterized by a boilingpoint greater than about 80° C. In this regard, low volatility for theelectrolyte solvent simplifies manufacture of the electrolyte/batteriesand improves their self-life.

If the solid polymeric matrix for the electrode is formed by radiationpolymerization of the solid matrix forming monomer or partial polymerthereof, then the solvent should be radiation inert at least up to thelevels of radiation employed. If the solid polymeric matrix is formed bythermal polymerization, the solvent should be thermally inert at leastup to the temperatures of thermal polymerization. Additionally, thesolvent should not scavenge free radicals.

Representative examples of suitable solvents include propylenecarbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, glyme(dimethoxyethane), diglyme, triglyme, tetraglyme, dimethylsulfoxide,dioxolane, sulfolane and the like, and mixtures thereof. A particularlypreferred solvent is a mixture of an organic carbonate and triglyme asdisclosed in U.S. patent application Ser. No. 07/918,509 filed asAttorney Docket No. 028574-026 and entitled "SOLID, SOLVENT-CONTAININGELECTROLYTES AND ELECTROLYTIC CELLS PRODUCED THEREFROM" whichapplication is incorporated herein by reference in its entirety.

The term "electrochemical cell" refers to primary and secondaryelectrochemical cells comprising an anode, a cathode, and anion-conducting electrolyte interposed therebetween. The ion-conductingelectrolyte can be either a liquid or a solid electrolyte but solidelectrolytes are preferred and more preferably, the electrochemical cellis a solid secondary cell.

The anode is typically comprised of a compatible anodic material whichis any material which functions as an anode in an electrochemical cell.Such compatible anodic materials are well known in the art and include,by way of example, lithium, lithium alloys, such as alloys of lithiumwith aluminum, mercury, nickel, zinc, and the like, and intercalationbased anodes such as carbon, WO₃, and the like.

The cathode comprises a compatible cathodic material which refers to anymaterial which functions as a positive pole (cathode) in anelectrochemical cell. Such compatible cathodic materials are well knownin the art and include, by way of example, manganese dioxide, molybdenumtrioxide, sulfides of titanium and niobium, chromium oxide, copperoxide, vanadium oxides such as V₂ O₅, V₆ O₁₃, LiV₃ O₈ and the like. Theparticular compatible cathodic material employed is not critical. Whenthe electrochemical cell is a secondary cell, then the compatiblecathodic material employed is one which is capable of being recharged(e.g., LiV₃ O₈, V₆ O₁₃, MoO₃, and the like).

The term "composite electrode" refers to cathodes and anodes wherein thecathode is comprised of materials other than compatible cathodicmaterials and the anode is comprised of materials other than compatibleanodic materials. Typically, the composite contains a polymer which actsto bind the composite materials together and an electrolytic solvent.

Composite cathodes are well known in the art. For example, a compositecathode can comprise a compatible cathodic material, a conductivematerial, an electrolytic solvent, an alkali salt, and a solid matrixforming polymer.

Composite anodes are also well known in the art. For example, acomposite anode can comprise a compatible intercalation anodic material,an electrolytic solvent and a solid matrix forming polymer.

Because polymers typically do not have sharply defined melting points,the term "liquid" as it applies to hot melts of polymers includespolymers in a condition where they can be mixed with a conductivematerial and, if necessary, a component or components containing acidfunctionality.

METHODOLOGY

The layer of electrically-conducting adhesion-promoter applied to thesurface of the conductive plastic foil is readily prepared by a varietyof methods.

Specifically, one method for preparing the layer ofelectrically-conducting adhesion-promoter is to use a suitableprepolymer which contains acid functionality. The preparation ofsuitable prepolymers containing acid functionality are well known in theart and certain of these prepolymers are commercially available. Forexample, acrylic acid, chloroacrylic acid, bromoacrylic acid, crotonicacid, and vinyl sulfonic acid are commercially available (e.g., fromAldrich Chemical Company) or are commercially available as salts whichcan be readily converted to the acid. The prepolymer can be used eitherby itself so as to provide for a homopolymer upon curing or can be usedwith other prepolymers to provide for a copolymer, terpolymer, etc. uponcuring. In this latter embodiment, it is necessary that only one of theprepolymers contain acid functionality.

Prepolymers containing acid functionality are typically liquid and arethen mixed either neat or in a solvent with a conductive material toprovide for a composition which is typically a paste or a colloidalsuspension. Suitable conductive materials are well known in the art andinclude, by way of example, carbon powder, graphite, powdered nickel,metal particles, conductive polymers (i.e., characterized by aconjugated network of double bonds like polypyrol and polyacetylene),and the like.

The resulting composition is then applied onto the surface of theconductive plastic foil. When a solvent is employed, it is removed byevaporation. The composition is cured by conventional techniques to forma solid layer of electrically-conducting adhesion-promoter on thesurface of the current collector. For example, when the prepolymercontains a reactive double bond, the composition can be cured bysuitable curing methods which include heating, irradiation with electronbeams (EB), etc. When the composition is cured by heating, thecomposition preferably contains an initiator which is typically aperoxide such as benzoyl peroxide, methyl ethyl ketone peroxide, t-butylperoxypyvarate, diisopropyl peroxycarbonate, and the like.

The initiator is generally employed in an amount sufficient to catalyzethe polymerization reaction. Preferably, the initiator is employed at upto about 1 weight percent based on the weight of the prepolymer.

When curing is by EB treatment, an initiator is not required.

In either case, the resulting solid polymeric matrix is a homogeneous,single phase material which is maintained upon curing, and does notreadily separate upon cooling to temperatures below room temperature.

Another method for preparing the layer of electrically-conductingadhesion-promoter is to employ an acid containing polymer derived from aprepolymer such as acrylic acid, chloroacrylic acid, bromoacrylic acid,crotonic acid, and vinyl sulfonic acid. The prepolymer can bepolymerized to form a homopolymer or copolymers, terpolymers, etc. bymethods well known in the art. As noted above, the prepolymer can beused either by itself so as to provide for a homopolymer upon curing orcan be used with other prepolymers to provide for a copolymer,terpolymer, etc. upon curing. In this latter embodiment, it is necessarythat only one of the prepolymers contain acid functionality.Additionally, it is possible to use a mixture of polymers in thecomposition. In this embodiment, it is necessary that only one of thepolymers is an acid containing polymer (e.g., a 1:1 mixture ofpolyethylene and polyacrylic acid).

The acid containing polymer is then mixed with a conductive material inany of a number of art recognized methods. For example, the polymer canbe dissolved into a suitable solvent, preferably an aprotic solvent, andthen the conductive material added. The resulting composition can thenbe applied to the surface of the conductive plastic foil and the solventevaporated to provide for a layer of electrically-conductingadhesion-promoter on the surface of the current collector. If a proticsolvent is employed, the resulting current collector is preferably driedat an elevated temperature for a prolonged period of time to reduce thelevel of protic solvent remaining in the electrically-conductingadhesion-promoter layer preferably to a level of less than about 30μg/cm² and more preferably less than 10 μg/cm² and even more preferablyless than about 5 μg/cm². The specific temperature used during thedrying step is selected relative to the electrically-conductingadhesion-promoter layer and conductive plastic current collectoremployed. In particular, the drying step is conducted at an elevatedtemperature below the melting point of both the adhesion-promoter layerand the conductive plastic current collector.

When a solvent is employed to dissolve the polymer used in theadhesion-promoter layer, it is of course selected to be inert to theconductive plastic current collector. For example, if the currentcollector contains polybutylene, then water can be used to dissolve apolymer such as polyacrylic acid which is used in the adhesion-promoterlayer.

Alternatively, the polymer containing the acid functionality can behot-melted at an elevated temperature and then the requisite amount ofconductive material is mixed into the polymer. The resulting compositionis then applied onto the conductive plastic foil and cooled to providefor a layer of electrically-conducting adhesion-promoter on the surfaceof the current collector. If a hot-melted polymer is employed, thetemperature of the hot melted polymer is selected so as not to melt theconductive plastic current collector.

Appropriate selection of the solvent or temperature of the meltedpolymer is well within the skill of the art.

Acid containing polymers are well known in the art and can be preparedby well known methods. In fact, some acid containing polymers arecommercially available. For example, several polyacrylic acids (ofvarying molecular weight) are commercially available from AldrichChemical Company, Milwaukee, Wis., as well as are polyvinylsulfonicacid, polyvinyl sulfate, poly(3hydroxybutyric acid) and copolymers ofpoly(3hydroxybutyric acid) and poly(3-hydroxyvaleric acid).Additionally, Sarbox resins, carboxylic acid containing resins, arecommercially available from Sartomer Chemicals, Exton, Pa.

Another method for preparing the layer of electrically-conductingadhesion-promoter is to modify a polymer not containing acidfunctionality so as to introduce acid functionality. Specifically,reactions resulting in the addition of carboxylic acid functionalityonto polymers are well known in the art. For example, the reaction ofmaleic anhydride with polymers containing a double bond such aspolybutene, polypropylene, polyalphaolefins, etc. is described in U.S.Pat. Nos. 3,018,250; 3,024,195; 4,234,435; 4,388,471; and 4,450,281.Each of these patents are incorporated herein by reference in theirentirety.

Additionally, free radical grafting of maleic anhydride, maleic acid,acrylic acid and methylacrylic acid onto polymers is also well known inthe art and is described in U.S. Pat. Nos. 4,857,600 and 4,810,755 aswell as in International Patent Application Publication No. WO 91/02760.Each of these references are incorporated herein by reference in theirentirety.

In either case, the reactions lead to either the incorporation of asingle succinic anhydride or maleic anhydride group or the incorporationof multiple such groups onto the polymer. The anhydride groups can thenbe hydrolyzed under suitable hydrolysis conditions to provide for thecorresponding acid functionalities.

Likewise, the addition of sulfonic acid groups to polymers of butylene,propylene, etc. are well known in the art.

After the acid functionality has been added to the polymer, the polymercan be mixed with a conductive material in the same manner describedabove with acid containing polymers.

In still another embodiment, a non-polymerizable component containingacid functionality (a non-polymeric acid component) can be added to apolymer or prepolymer to form a composite comprising the non-polymericacid component, the polymer, and the conductive material. Specifically,a nonpolymeric acid component can be added directly to the compositionof the prepolymer and the conductive material. The resulting compositionis then applied to the surface of the conductive plastic foil and curedso as to provide for a layer of electrically-conductingadhesion-promoter on the surface of the foil.

Alternatively, the non-polymeric acid component can be mixed in ahot-melt of a polymer or dissolved into a mutual solvent (preferably anaprotic solvent) with the polymer. After addition of the conductivematerial, a layer of the resulting mixture is applied onto the substratevia conventional techniques (e.g., extrusion, roll coating, etc.).Cooling or evaporation then affords a layer of electrically-conductingadhesion-promoter on the surface of the current collector. If a proticsolvent is employed, evaporation is preferably conducted at an elevatedtemperature for a prolonged period of time to reduce the level of proticsolvent in the electrically-conducting adhesion-promoter layer.

Preferably, the non-polymeric acid component has a boiling point ofgreater than about 80° C. and is compatible with the polymer. Theparticular acid-containing, non-polymeric component employed is notcritical and includes, by way of example, stearic acid, palmitic acid,oleic acid, succinic acid, maleic acid, monodiol diphosphoric acid,phthalic acid, 1-hexadecane sulfonic acid, and the like.

Regardless of the method in which the acid functionality is incorporatedinto the composition, sufficient acid functionality is incorporated soas to enhance the adherence of the layer of the electrically-conductingadhesion-promoter to the surface of the conductive plastic foil andsufficient conductive material is added to render the resulting solidpolymeric matrix electrically conducting.

Preferably, the amount of conductive material employed is from about 30to about 80 weight percent of the composition and more preferably, fromabout 40 to about 60 weight percent of the composition.

Preferably, sufficient acid functionality is incorporated into thiscomposition so that the composition has an acid number of at least 0.01milliequivalents per gram and, more preferably, from about 1 to about250 milliequivalents per gram, and even more preferably, from about 10to about 150 milliequivalents per gram.

The term "acid number" refers to the amount of acid equivalent inmilliequivalents of proton in 1 gram of the composition and is reportedas milliequivalents per gram. The acid number for this composition isreadily determined by ASTM test number D664.

The layer of electrically-conducting adhesion-promoter is applied bywell known conventional techniques onto the conductive plastic foil. Forexample, pastes can be applied by extrusion whereas dispersed colloidalsolutions can be applied by dipping, painting, spraying, gravuring, rollcoating, including reverse roll coating, doctor blades, and the like.The particular method employed is not critical.

After application, the layer of electrically-conductingadhesion-promoter is treated to convert this layer to a solid,electrically-conducting, polymeric matrix. Such conversion isaccomplished by reference to the layer applied. For example, if thelayer contains a prepolymer, then the conversion includes a curing stepto convert the prepolymer to a polymer so as to provide for the solid,polymeric matrix. Likewise, if the layer contains a polymer in solution,then the conversion includes an evaporation step wherein the solvent isremoved so as to provide for the solid, polymeric matrix. Lastly, if thelayer contains a hot-melted polymer, then the conversion includes acooling step wherein the polymeric composition is solidified so as toprovide for the solid, polymeric matrix.

After conversion, the resulting solid polymeric matrix preferably has athickness of from at least one molecule to no more than about 100 μm.More preferably, this matrix has a thickness of from about 100 Angstromsto about 20 μm in thickness and even more preferably is from about 0.1μm to about 10 μm in thickness.

Preferably, the polymer in the solid polymeric matrix has a molecularweight of at least about 10,000 regardless of whether the polymer isformed in situ or if a preformed polymer is used to prepare the layer ofelectrically-conducting adhesion-promoter. More preferably, the polymerhas a molecular weight of at least about 50,000 and still morepreferably has a molecular weight of at least about 90,000. The upperlimit for the molecular weight of the polymer is not critical butpreferably is no more than about 5,000,000.

After formation of the solid polymeric matrix, electrically-conducting,adhesion-promoter layer on the surface of the current collector, acomposite electrode is then applied thereto. The electrode is typicallyprepared from an electrode paste. For example, a cathodic paste can beprepared by combining from about 1 to about 20 weight percent of aconductive material, from about 35 to about 60 weight percent of acompatible cathodic material, from about 10 to about 50 weight percentof an electrolytic solvent and from about 5 to 30 weight percent of acathode prepolymer all based on the total weight of the cathode paste.

Suitable conductive materials include by way of example, carbon powder,graphite, powdered nickel, metal particles, conductive polymers (i.e.,characterized by a conjugated network of double bonds like polypyrol andpolyacetylene), and the like.

Suitable cathode prepolymers are well known in the art and preferablyare alkali or alkaline earth metal ion conducting. Suitable cathodeprepolymers include, by way of example, propylene oxide, ethyleneimine,ethylene oxide, epichlorohydrin, acryloyl-derivatized polyalkyleneoxides (as disclosed in U.S. Pat. No. 4,908,283), urethane acrylates,vinyl sulfonate polyalkylene oxides (as disclosed in U.S. Pat. No.5,262,253 which patent is incorporated herein by reference in itsentirety), and the like as well as mixtures thereof.

The cathode paste can optionally contain film forming agents which arewell known in the art and include, by way of example, polyethyleneoxide, polypropylene oxide, copolymers thereof, and the like, having anumbered average molecular weight of at least about 100,000. Preferably,the film forming agent is employed in an amount of about 1 to about 10weight percent and more preferably at about 2.5 weight percent based onthe total weight of the cathode composition.

The cathode paste so formed is preferably heat treated prior toapplication onto the current collector by exposing the paste to anelevated temperature as described in U.S. Ser. No. 07/968,203 filedconcurrently herewith as Attorney Docket No. 1116 and entitled "METHODSFOR ENHANCING THE COATABILITY OF CARBON PASTES TO SUBSTRATES" whichapplication is incorporated herein by reference in its entirety.Preferably, the temperature employed to heat treat the paste is fromabout 60° to about 130° C. and more preferably from about 80° to about90° C. Preferably, the paste is heated for a period of from about 0.1 toabout 2 hours, more preferably from about 0.1 to about 1 hour, and evenmore preferably from about 0.2 to about 1 hour. In a particularlypreferred embodiment, the paste is heat treated at from about 80° toabout 90° C. for about 0.33 to about 0.5 hours.

The electrolytic solvent employed in the cathode paste is not criticalbut preferably is a 10:1 to 1:10 mixture of ethylene and/or propylenecarbonate to triglyme. Preferred mixtures include a 4:1 mixture ofethylene and/or propylene carbonate to triglyme and a 1:1 mixture ofethylene and/or propylene carbonate to triglyme. See, for example, U.S.Ser. No. 07/918,509 filed Jul. 22, 1992 which is incorporated herein byreference in its entirety.

Anode pastes can also be prepared using known methods. Anode pastes cancomprise from about 1 to about 20 weight percent of a conductivematerial, from about 35 to about 60 weight percent of a compatibleanodic material, from about 10 to about 50 weight percent of anelectrolytic solvent and from about 5 to about 30 weight percent of ananode prepolymer (similar to cathode prepolymers) all based on the totalweight of the paste.

As described above, the electrode paste (i.e., the cathode or anodepaste) is then applied onto the surface of the layer ofelectrically-conducting adhesion-promoter which, in turn, is found onthe surface of a conductive plastic foil. The electrode paste is thencured to provide for the solid electrode.

When the electrode paste is a cathode paste, it is preferably appliedonto the layer of electrically-conducting adhesion-promoter at a rate togive, after curing, a substantially uniform coating thickness of fromabout 20 to about 150 microns. Similarly, when the electrode paste is ananode paste, it is preferably applied onto the layer ofelectrically-conducting adhesion-promoter at a rate to give, aftercuring, a substantially uniform coating thickness of from about 20 toabout 150 microns.

Curing is generally accomplished by conventional techniques to form asolid electrode. For example, suitable curing methods include heating,irradiation with electron beams (EB), etc. When the composition is curedby heating, the composition preferably contains an initiator. Forexample, heat curing initiators are typically peroxides such as benzoylperoxide, methyl ethyl ketone peroxide, t-butyl peroxypyvarate,diisopropyl peroxycarbonate, and the like.

The initiator is generally employed in an amount sufficient to catalyzethe polymerization reaction. Preferably, the initiator is employed at upto about 1 weight percent based on the weight of the solid matrixforming monomer.

When curing is by EB treatment, an initiator is not required.

In either case, the resulting cured electrode is a solid, homogeneous,single-phase material which is maintained upon curing, and does notreadily separate upon cooling to temperatures below room temperature.See, for example, U.S. Pat. No. 4,925,751 which is incorporated hereinby reference in its entirety.

Accordingly, the resulting product is a composite containing aconductive plastic foil which functions as a current collector, a layerof electrically-conducting adhesion-promoter, and a composite electrode(i.e., a composite cathode or composite anode) wherein the layer ofelectrically-conducting adhesion-promoter is interposed between the foiland the electrode.

As an additional matter, it is preferable to avoid the use of any proticmaterials which will be incorporated into the battery. For example, mostof the protic inhibitors in di- and triacrylate prepolymers as well asin the urethane acrylate prepolymers are preferably removed prior toformation of the layer of electrically-conducting adhesion promoter, thecomposite electrode and/or the electrolyte. In this regard, removal ofthese inhibitors down to a level of less than 50 parts per million (ppm)can be accomplished by contacting these monomers and prepolymers with aninhibitor remover. Suitable inhibitor removers are commerciallyavailable.

An electrochemical cell is then formed using the currentcollector/electrode so formed. For example, if the electrode is acomposite cathode, then the electrochemical cell is formed by combiningthe cathode with an anode and an electrolyte interposed therebetween.

Preferably, the electrochemical cell employs a solid, homogeneous,single-phase electrolyte which is maintained upon curing, and which doesnot readily separate upon cooling to temperatures below roomtemperature. See, for example, U.S. Pat. No. 4,925,751 which isincorporated herein by reference in its entirety. Such solid, singlephase electrolytic compositions are formed from a liquid compositioncontaining a polymerizable electrolyte prepolymers which upon curingprovides for the solid, single phase material.

In this regard, the liquid electrolyte composition containing suchprepolymers are preferably applied over a layer of cathode paste whichitself is formed over a layer of electrically-conductingadhesion-promoter found on a conductive plastic foil. Both the cathodepaste and the liquid electrolyte composition are preferably curedsimultaneously by exposure to, for example, electron beams so as toprovide for a cured composite containing both the cured cathode and thecured electrolyte. Alternatively, the liquid electrolyte can be appliedto the cured cathode and then itself cured in a step separate from thecathode curing step.

The solid, single-phase electrolyte has a thickness of no more thanabout 250 microns (μm). Preferably, the solid, solvent-containingelectrolyte has a thickness of from about 10 to about 250 microns, morepreferably from about 25 to about 150 microns, and even more preferablyfrom about 40-80 microns.

Utility

The electrically-conducting adhesion-promoter of this invention isuseful in enhancing the adherence of the electrode to the currentcollector of an electrochemical cell. Specifically, theelectrically-conducting adhesion-promoter is interposed between theelectrode and the current collector. Because of its acid functionality,this adhesion-promoter effectively adheres to the current collector.Additionally, the surface of this layer of adhesion-promoter ischaracterized on a microscopic level by peaks and valleys which enhancethe adhesion of the electrode to this layer.

The improved adherence of the conductive plastic foil to the electrodeby the use of the electrically-conducting adhesion-promoter layerdescribed herein is evidenced by the reduced rate at which the electrodepaste separates from this layer during application as compared to therate of separation arising from use of a conductive plastic foil withoutthis layer. This improved adhesion of the electrode paste to the currentcollector by virtue of the interposed layer of electrically-conductingadhesion-promoter can be quantified as per ASTM test number D-3359-87.

Since this adhesion-layer is electrically-conducting, the currentgenerated by the electro-chemical cell can pass through it and becollected by the conductive plastic foil acting as the currentcollector.

When the layer of electrically-conducting adhesion-promoter ispreferably non-cation conducting, then migration of alkali or alkalineearth metal cations to the current collector is prevented. This, inturn, prevents potentially adverse interaction of such cations with thecurrent collector (e.g., corrosion) which could reduce the useful lifeof the electrochemical cell.

The following examples are offered to illustrate the present inventionand should not be construed in any way as limiting its scope.

EXAMPLES Example 1

An electrically-conducting, adhesive promoter is first formulated as adispersed colliodal solution. The formulation for this example was asfollows:

171 grams of carbon powder (Shawinigan Black--available from ChevronChemical Company, San Ramon, Calif.)

2727 grams of distilled water

3250 grams of isopropanol

684 grams of a 25 weight percent solution of polyacrylic acid (averagemolecular weight of about 90,000, commercially available from AldrichChemical Company)

The carbon powder, water and isopropanol are mixed in a conventionalhigh shear colloid mill mixer until the carbon is uniformly dispersed.At this point, the 25 weight percent solution of polyacrylic acid isadded to the solution and mixed. If necessary, mixing can be enhanced byan ink mill and the degree of mixing quantified by use of a Hegmangauge.

The resulting mixture is roll coated onto a sheet of Southwall SilverReflector Film (a conductive plastic film available from SouthwallTechnologies, Palo Alto, Calif.). A uniform coating is obtained.Evaporation of the solvents (i.e., water and isopropanol) provides foran electrically-conducting adhesion promoter layer of about 12 micronsin thickness. In order to further remove the protic solvent from thislayer, the foil can be redried. For example, redrying can be conductedby placement of the foil in an oven maintained at about 130° C. or moreover a period of time (e.g., 12 to 24 hours).

Example 2

A second electrically-conducting, adhesive promoter is formulated as adispersed colliodal solution. The formulation for this example is asfollows:

84.4 grams of carbon powder (Shawinigan Black™--available from ChevronChemical Company, San Ramon, Calif.)

337.6 grams of a 25 weight percent solution of polyacrylic acid (averagemolecular weight of about 90,000, commercially available from AldrichChemical Company--contains about 84.4 grams polyacrylic acid and 253.2grams water)

578 grams of isopropanol

The carbon and isopropanol are mixed in a conventional high shearcolloid mill mixer until the carbon is uniformly dispersed. At thispoint, the 25 weight percent solution of polyacrylic acid is added tothe solution and mixed. The resulting mixture is roll coated with aMeyer rod onto a sheet of Southwall Silver Reflector Film, a conductiveplastic film available from Southwall Technologies, Palo Alto, Calif.After application, the solution/foil are contacted with a Mylar wipe(about 0.002 inches thick by about 2 inches and by about 9 inches wide).The wipe is flexibly engaged with the foil (i.e., the wipe merelycontacted the foil) to redistribute the solution so as to provide for asubstantially uniform coating. Evaporation of the solvents (i.e., waterand isopropanol) via a conventional gas-fired oven provides for anelectrically-conducting adhesion-promoter layer.

In order to further remove the protic solvent from the layer, the foilis redried. In particular, the foil is wound up and a copper supportplaced through the roll's cavity. The roll is then hung overnight fromthe support in a vacuum oven maintained at about 130° C. Afterwards, theroll is removed. In order to avoid absorption of moisture from theatmosphere, the roll is preferably placed into a desiccator or othersimilar anhydrous environment to minimize atmospheric moisture content.

Example 3

A third electrically-conducting, adhesive promoter is formulated as adispersed colloidal solution. The formulation for this example is asfollows:

84.4 grams of carbon powder (Shawinigan Black™--available from ChevronChemical Company, San Ramon, Calif.)

64.4 grams of polyethylene oxide (MW about about 100,000, commerciallyavailable from Aldrich Chemical Company)

80.0 grams of a 25 weight percent solution of polyacrylic acid (averagemolecular weight of about 90,000, commercially available from AldrichChemical Company--contains about 20 grams polyacrylic acid and 60 gramswater)

578 grams of isopropanol

The carbon and isopropanol are mixed in a conventional high shearcolloid mill mixer until the carbon is uniformly dispersed. At thispoint, the 25 weight percent solution of polyacrylic acid is added tothe solution and mixed. The polyethylene oxide is then added and, ifnecessary, additional water is added to dissolve all of the polyethyleneoxide. After mixing, the resulting mixture is roll coated with a Meyerrod onto a sheet of Southwall Silver Reflector Film. After application,the solution/foil is contacted with a Mylar wipe. The wipe is flexiblyengaged with the foil (i.e., the wipe merely contacted the foil) toredistribute the solution so as to provide for a substantially uniformcoating. Evaporation of the solvents (i.e., water and isopropanol) via aconventional gas-fired oven provides for an electrically-conductingadhesion-promoter layer.

In order to remove additional protic solvent from the layer, the foil isredried. In particular, the foil is wound up and a copper support placedthrough the roll's cavity. The roll is then hung overnight from thesupport in a vacuum oven maintained at about 130° C. Afterwards, theroll is removed. In order to avoid absorption of moisture from theatmosphere, the roll is preferably placed into a desiccator or othersimilar anhydrous environment to minimize atmospheric moistureadsorption.

Example 4

A fourth electrically-conducting, adhesive promoter is formulated as apolymer hot-melt. The formulation for this example is as follows:

84.4 grams of carbon powder (Shawinigan Black™--available from ChevronChemical Company, San Ramon, Calif.)

64.4 grams of polyethylene oxide (MW about about 100,000, commerciallyavailable from Aldrich Chemical Company.

20.0 grams of stearic acid

The polyethylene oxide is hot melted and then the carbon powder andstearic acid are mixed until uniformly dispersed. While maintaining aliquid state, the resulting mixture is extruded onto a sheet ofSouthwall Silver Reflector film. After extrusion, the foil is cooled toroom temperature, preferably under anhydrous conditions, so as toprovide for a solid, electrically-conducting, adhesion-promoter layer ofabout 10 microns in thickness on the foil. In order to avoid absorptionof moisture from the atmosphere, the roll is preferably placed into adesiccator or other similar anhydrous environment to minimizeatmospheric moisture adsorption.

Example 5

A fifth electrically-conducting, adhesive promoter is formulated as adispersed colloidal solution. The formulation for this example is asfollows:

84.4 grams of carbon powder (Shawinigan Black™--available from ChevronChemical Company, San Ramon, Calif.)

345.0 grams of a 25 weight percent solution of vinylsulfonic acid[commercially available from Aldrich Chemical Company as the sodium salt(337.6 grams) which is converted to the acid by contact with aconcentrated HCl aqueous medium--contains about 84.4 grams vinylsulfonicacid, and balance water]

578 grams of isopropanol

578 grams of isopropanol

The carbon and isopropanol are mixed in a conventional high shearcolloid mill mixer until the carbon is uniformly dispersed. At thispoint, the 25 weight percent solution of polyvinyl sulfonic acid isadded to the solution and mixed. If desired, the hydroquinone monomethylether inhibitor can be removed from the polyvinyl sulfonic acid prior toaddition to the carbon/iso-propanol mixture. Such removal is effected bycontacting this solution with an Inhibitor Remover available as ProductNo. 31,133-2 from Aldrich Chemical, Milwaukee, Wis. which results inless than 50 ppm of inhibitor in the product.

The resulting colloidal suspension is then roll coated with a Meyer rodonto a sheet of Southwall Silver Reflector Film. After application, thesolution/foil is contacted with a Mylar wipe. The wipe is flexiblyengaged with the foil (i.e., the wipe merely contacted the foil) toredistribute the solution so as to provide for a substantially uniformcoating.

The solvent is evaporated at about 110° to 120° C. via a conventionalgas-fired oven and the remaining layer is then cured by continuouslypassing the foil through an electron beam apparatus (Electrocurtain,Energy Science Inc., Wolburn, Mass.) at a voltage of about 175 kV and acurrent of about 1.0 mA and at a conveyor belt speed setting of 50 whichprovides a conveyor speed of about 1 cm/sec so as to provide for anelectrically-conducting adhesion-promoter layer on the foil.

In order to remove additional protic solvent from the layer, the foil isredried. In particular, the foil is wound up and a copper support placedthrough the roll's cavity. The roll is then hung overnight from thesupport in a vacuum oven maintained at about 130° C. Afterwards, theroll is removed. In order to avoid absorption of moisture from theatmosphere, the roll is preferably placed into a desiccator or otherequivalent anhydrous solvent to minimize atmospheric moistureadsorbtion.

Example 6

An electrically-conducting, adhesive promoter was first formulated as adispersed colliodal solution. The formulation for this example was asfollows:

25 lbs of carbon powder (Shawinigan Black--available from ChevronChemical Company, San Ramon, Calif.)

18.5 lbs of isopropanol

100 lbs of a 25 weight percent solution of polyacrylic acid (averagemolecular weight of about 90,000, commercially available from AldrichChemical Company)

The carbon powder was mixed directly with the total amount ofpolyacrylic acid and 25% of the isopropanol (18.5 lbs). The mixture wasstirred with a gear-motor "Lightin" mixer (model XJ-43--available fromMixing Equipment Co., Avon, N.Y.) at 720 rpms with two 5 inch diameterA310-type propellors mounted on a single shaft in a 30 gallonpolyethylene drum which wets the carbon and eliminates any further dustproblem. The resulting composition ("master batch") is 143.5 lb andcontains some lumps.

The master batch was then mixed in an ink mill which consists of threesteel rollers almost in contact with each other, turning at 275, 300 and325 rpms, respectively. This high shear opertion allowed particles thatwere sufficiently small to pass directly through the rollers. Those thatwere not continued to be mixed until they can pass through the rollers.When mixing was completed, the the carbon was completely dispersedthroughout the composition. A Hegman fineness of grind gauge (availablefrom Paul N. Gardner Co., Pompano Beach, Fla.) indicates that theparticles were typically about 4-6 μm in diameter with an ocassionalparticle of about 12.5 μm in diameter. Prolonged storage of the mixturedid not result in carbon settling out or in reagglomeration.

Prior to roll coating this mixture, the remaining 75% of the isopropanolwas mixed in, working with 5 gallon batches in a plastic pail. This wasaccomplished using an air powered shaft mixer (Dayton model 42231available from Granger Supply Co., San Jose, Calif.) with a 4 inchdiameter Jiffy-Mixer brand Impeller. Then, the mixture was gear-pumpedthrough a 125 μm cloth filter.

At this point the mixture is Meyer-rod coated onto a conductive plasticsubstrate in a manner similar to that described in Example 2 above.

EXAMPLE 7

A current collector containing an electrically-conductingadhesion-promoter is prepared in the manner described in Example 2above. A cathode paste is then applied to the surface of theelectrically-conducting adhesion-promoter. The cathode paste is preparedfrom a cathode powder as follows:

i. Cathode Powder

The cathode powder is prepared by combining 90.44 weight percent V₆ O₁₃[prepared by heating ammonium metavanadate (NH₄ ⁺ VO₃ ⁻) at 450° C. for16 hours under N₂ flow] and 9.56 weight percent of carbon powder (fromChevron Chemical Company, San Ramon, Calif. under the tradename ofShawinigan Black™). About 100 grams of the resulting mixture is placedinto a grinding machine (Attritor Model S-1 purchased from UnionProcess, Akron, Ohio) and ground for 30 minutes. Afterwards, theresulting mixture is dried at about 260° C. for 16 hours to provide acathode powder having about 84.45 weight percent V₆ O₁₃.

The above mixing procedure is repeated until the entire sample is mixedso as to provide for 292 grams of cathode powder.

ii. Cathode Paste

A cathode paste is prepared by combining sufficient cathode powder toprovide for a final product having 45 weight percent V₆ O₁₃.

Specifically, about 28.71 grams of unground carbon powder (from ChevronChemical Company, San Ramon, Calif. under the tradename of ShawiniganBlack™) is combined in a glove box [under dry (<10 ppm H₂ O) argon atambient temperature and pressure] with about 57.2 grams of a 1:1 mixtureof ethylene carbonate/triglyme and the resulting composite is mixedunder dry argon and at ambient temperature and pressure on a doubleplanatory mixer (Ross #2 mixer available from Charles Ross & Sons,Company, Hauppag, N.Y.) at about 20 rpms until a paste is formed.

About 248.77 grams of a cathode powder prepared in a manner similar tothat described above is added to the mixer along with an additional 57.2grams of a 1:1 mixture of triglyme/ethylene carbonate and the resultingcomposite is mixed under dry argon and at ambient temperature andpressure on a double planatory mixer at about 20 rpms until a dry pasteis formed.

About 5 grams of polyethylene oxide (number average molecular weightabout 600,000 available as Polyox WSR-205 from Union Carbide Chemicalsand Plastics, Danbury, Conn.), about 42.9 grams of polyethylene glycoldiacrylate (PEGDA) (molecular weight about 400 available as SR-344 fromSartomer Company, Inc., Exton, Pa.) and containing less than about 50ppm of inhibitor, and about 7.6 grams of ethoxylated trimethylpropanetriacylate (TMPEOTA) (molecular weight about 450 available as SR-454from Sartomer Company, Inc., Exton, Pa.) and containing less than about50 ppm of inhibitor are added to about 57.2 grams of a 1:1 mixture oftriglyme/ethylene carbonate and this mixture is added to the mixer.

The resulting slurry in the mixer is heated at about 65° C. while mixingfor 2 hours at 60 rpms to provide for the cathodic paste which had thefollowing approximate weight percent of components:

    ______________________________________                                        V.sub.6 O.sub.13 45       weight percent                                      Carbon           10       weight percent                                      ethylene carbonate/tri-                                                                        34       weight percent                                      glyme                                                                         polyethylene oxide                                                                             1        weight percent                                      polyethylene glycol                                                                            8.5      weight percent                                      diacrylate.sup.1                                                              ethoxylated trimethyl-                                                                         1.5      weight percent                                      propane triacrylate.sup.1                                                     ______________________________________                                         .sup.1 Inhibitor is removed from both the polyethylene glycol diacrylate      and ethoxylated trimethylpropane triacrylate by contacting each of these      compounds with an Inhibitor Remover available as Product No. 31,1332 from     Aldrich Chemical, Milwaukee, Wisconsin which results in less than 50 ppm      of inhibitor in the product.                                             

In an alternative embodiment, the requisite amounts of all of thecathodic materials other than the cathode powder can be combined to forma first mixture and this first mixture is combined with the cathodepowder to form a second mixture. This second mixture is then thoroughlymixed to provide for the cathode paste.

The cathode paste prepared as above is then heat treated at about 85° C.for about 20 minutes so as to enhance its adhesiveness, its softness andits electrolytic solvent retention properties.

The cathode paste is then placed onto the surface of theelectrically-conducting adhesion-promoter attached to the currentcollector prepared in Example 2. A Mylar cover sheet is then placed overthe paste and the paste is spread to thickness of about 90 microns (μm)with a conventional plate and roller system and cured.by continuouslypassing the sheet through an electron beam apparatus (Electrocurtain,Energy Science Inc., Wolburn, Mass.) at a voltage of about 175 kV and acurrent of about 1.0 mA and at a conveyor belt speed setting of 50 whichprovides a conveyor speed of about 1 cm/sec. After curing, the Mylarsheet is removed to provide for a solid cathode laminated to a nickel onnickel current collector.

B. Electrolyte

A solid electrolyte is prepared in the manner described in U.S. Ser.Nos. 07/918,508 and 07/918,509 both filed Jul. 22, 1992 and both ofwhich are incorporated herein by reference. Specifically, about 137.48grams of a 1:1 mixture of ethylene carbonate/triglyme and about 34.26grams of urethane acrylate (available as Photomer 6140 from HenkelCorporation, Coating and Chemicals Division, Ambler, Pa.) are firstcombined. The resulting solution is passed through a column of InhibitorRemover (available as Product No. 31,133-2 from Aldrich Chemical,Milwaukee, Wisc.) and then through a column of 4A molecular sieves toremove water.

This solution is then combined with about 5.02 grams of polyethyleneoxide (number average molecular weight about 600,000 available as PolyoxWSR-205 from Union Carbide Chemicals and Plastics, Danbury, Conn.). Oncethe polyethylene oxide is dispersed, about 23.24 grams of LiAsF₆(available from FMC Corporation Lithium Division, Bessemer City, N.C.,as Lectrosalt™) is added while stirring with a laboratory mixer (YamatoModel LR41B, available from Fisher Scientific, Santa Clara, Calif.).Alternatively, the salt can be added before the polyethylene oxide (PEO)and then, after dissolution of the salt, the PEO can be added andstirred until dispersed.

The resulting 200 gram mixture contains the following weight percent ofcomponents:

ethylene carbonate 34.37 weight percent

triglyme 34.37 weight percent

polyethylene oxide 2.51 weight percent

urethane acrylate 17.13 weight percent

LiAsF₆ 11.62 weight percent

The mixture is then thoroughly mixed with the same laboratory mixer atheating until a temperature of about 85° C. is reached and then cooledto ambient temperature over at least a 2 hour period while stirring ismaintained. This mixture is then placed into a vacuum (at about 0.1torr) for about 30 minutes.

Afterwards, the electrolyte mixture is then coated by a conventionalknife blade to a thickness of about 50 μm onto the surface of thecathode sheet prepared as above (on the side opposite that of thecurrent collector) but without the Mylar covering. The electrolyte isthen cured by continuously passing the sheet through an electron beamapparatus (Electrocurtain, Energy Science Inc., Wolburn, Mass.) at avoltage of about 175 kV and a current of about 1.0 mA and at a conveyorspeed setting of 50 which provides for a conveyor speed of about 1cm/sec. After curing, a composite is recovered which contained a solidelectrolyte laminated to a solid cathode which, in turn, is laminated toa nickel on nickel current collector.

C. Anode

The anode comprises a sheet of lithium foil (about 76 μm thick) which iscommercially available from FMC Corporation Lithium Division, BessemerCity, N.C.

D. The Solid Battery

A sheet comprising a solid battery is prepared by laminating the lithiumfoil anode to the surface of the electrolyte in the sheet produced instep C above. Lamination is accomplished by minimal pressure.

The above examples are illustrative of this invention. It beingunderstood, however, that this invention is not limited to theseexamples and that equivalent materials can be substituted therein. Forexample, polymers other than polyacrylic acid, polyoxyethylene oxide,and polyvinyl sulfonic acid used in the electrically-conductingadhesion-promoter layer such as maleic anhydride grafted polymers (e.g.,polybutene, polypropylene, or copolymers of polyethylene and methylacrylates, and the like), copolymers of acrylic acid with other solidmatrix forming monomers (e.g., ethylene, propylene, butylene, and thelike), etc. can be used in these examples by mere substitution for thepolymer so used.

Likewise, other non-polymeric acid containing components can be used inplace of stearic acid in Example 4 by mere substitution for the stearicacid so used. Such other non-polymeric acid containing componentsinclude, by way of example, abietic acid, decanoic acid, linolenic acid,palmitic acid, oleic acid, succinic acid, maleic acid, menadioldiphosphoric acid, phthalic acid, and 1-hexadecane sulfonic acid.

Still further, other conductive materials can be used in place of theShawinigan Black™ carbon powder used in the above examples by meresubstitution for the carbon powder so used. Such other conductivematerials include, by way of example, graphite, powdered nickel, metalparticles, conductive polymers (i.e., characterized by a conjugatednetwork of double bonds like polypyrol and polyacetylene), and the like.

What is claimed is:
 1. An electrode/current collector compositecomprising:a conductive plastic foil suitable for use as a currentcollector; a layer of a solid polymeric matrix, electrically-conducting,adhesion-promoter formed on at least one surface of the foil whichcomprises from about 30 to 80 weight percent of a conductive material;from about 20 to about 70 weight percent of a polymer derived from asolid matrix forming monomer or partial polymer thereof; and aneffective amount of acid functionalities so as to enhance the adherenceof this layer of electrically-conducting adhesion-promoter to thesurface of the foil; and a composite electrode paste selected from thegroup consisting of a cathode paste and an anode paste, wherein thecathode paste comprises from about 1 to about 20 weight percent of aconductive material, from about 35 to about 60 weight percent of acompatible cathodic material, from about 10 to about 50 weight percentof an electrolytic solvent and from about 5 to 30 weight percent of acathode prepolymer all based on the total weight of the paste, andfurther wherein the anode paste comprises from about 1 to about 20weight percent of a conductive material, from about 35 to about 60weight percent of a compatible anodic material, from about 10 to about50 weight percent of an electrolytic solvent and from about 5 to about30 weight percent of an anode prepolymers all based on the total weightof the paste wherein said adhesion-promotor is interposed between saidplastic foil and said composite electrode.
 2. The electrode/currentcollector according to claim 1 wherein said composite electrode is acomposite cathode.
 3. The electrode/current collector according to claim1 wherein said composite electrode is a composite anode.